It has been well-understood that the central process unit (CPU), dynamic random access memory (DRAM), graphic chip, and chip set in a computer system use different working voltages. Therefore, it requires a number of DC-DC converters in a computer system to convert the DC input voltage provided by power supply into the regulated working voltage required by each element.
A conventional DC-DC converter comprises an error amplifier, a pulse width modulation (PWM) comparator, a driver, and a power switch. The error amplifier is configured to compare the output voltage of the converter with a reference voltage. The PWM comparator is configured to receive the output from the error amplifier, and receive a sawtooth signal (also known as triangular wave signal or ramp signal) as input. The PWM comparator output a PWM signal, which is received by the driver to drive the power switch. Although the conventional DC-DC converter has the advantage of having a simple structure, but the compensation required by the amplifier will result in a slow transient response to load.